1. Field of the Invention
The present invention relates to an organic light emitting diode, and more particularly, to an electrode with a moisture-absorbing material.
2. Description of the Related Technology
Typically, an organic light emitting display, among flat panel displays, is not easily affected by impact or vibration, and has a wide temperature usage range, a wide viewing angle, and a fast response speed to provide a clear moving picture compared to other flat panel displays, so that it has attracted attention as a next generation flat panel display.
Such an organic light emitting display may be classified into a passive matrix type and an active matrix type. The passive matrix type requires a drive source located outside the display area while the active matrix type has thin film transistors (TFT) located in the display area as switching elements.
In an active matrix organic light emitting display, each pixel is driven by a TFT as a switching element so that a voltage supplied to each pixel can be completely independent from each other and may be persistent. Thus, the active matrix organic light emitting display has many advantages such as high resolution, high image quality, large area implementation and so forth.
Additionally, the organic light emitting display may be classified as a bottom emission configuration and a top emission configuration. In the bottom emission configuration, light is emitted through the substrate, on which the display device is built. On the other hand, in the top emission configuration, light is emitted in a direction away from the substrate. In some configurations, the organic light emitting display may emit light in directions through and away from the substrate.
FIG. 1 is a cross-sectional view of an exemplary bottom-emission organic light emitting diode, which forms a pixel or subpixel of the organic light emitting display. In the organic light emitting diode, a first or transparent electrode 110 is formed on a substrate 100. The first electrode 110 may be formed of a transparent material such as indium tin oxide (ITO), indium zinc oxide (IZO), and In2O3.
Subsequently, an organic layer 120 is formed on the first electrode 110. The organic layer contains a light emitting material. In addition to the light emitting layer, the organic layer may include at least one of an electron injection layer, an electron transport layer, a hole injection layer, a hole transport layer, and a hole block layer.
Subsequently, a second or reflective electrode 130 is formed on the organic layer 120 to complete the formation of the organic light emitting diode. The second electrode 130 may be formed of a reflective material such as Ca, Mg, MgAg, Ag, an Ag alloy, Al, and an Al alloy.
Next, the drive source is included in the organic light emitting diode and then an encapsulation process is carried out to finish an organic light emitting display.
In the above-described organic light emitting display, Al or Al alloy is typically employed in a single layer for the second or reflective electrode. Without an extra desiccant or getter, however, Al or Al alloy has insufficient resistance against the penetration of moisture (H2O) and/or oxygen (O2), and thus pixel shrinkage or dark spot defects may easily occur unless a moisture absorbing material is used an encapsulation substrate in the encapsulation process. The foregoing discussion is to provide description of related technology and does not constitute an admission of prior art.